There is specificity of California serogroup bunyaviruses for particular mosquitoes. Because of this vector specificity even when two human encephalitis viruses such as La Crosse and Jamestown Canyon exist in the same area, they maintain separate life cycles. The recently introduced non-native mosquito Aedes albopictus can be infected with both viruses. Moreover, this mosquito is colonizing many areas of the United States where both viruses are present. It seems reasonable to assume that this mosquito will become infected with both viruses and this co-infection will result in the generation of JC/LACV reassorted viruses. The long term goal of the proposed research is to understand the interaction of a bunyavirus with its mosquito vector. Specifically, the research aims are: 1) to determine the genetic basis for differences in insect transmission of lACV and JCV by the use of reassorted viruses 2) to determine the requirement of genome segments in infection, amplification and neuropathology in mammals 3) to identify epitopes on lACV G2 responsible for attachment of the virus to mosquito cells and determine the amino acid sequences involved and to examine other bunyaviruses for similar epitopes. Moreover, these reassortants may have a significant public health threat and examination of these viruses and their vector should allow us to assess this risk. Future studies may exploit this knowledge for the prevention of bunyavirus diseases using techniques such as transgenic mosquitoes.